This invention relates to a continuous process for making heather yarn by combining polyester and polyamide continuous filament yarns, followed by false twist texturing and drawing the combined yarns in a false twist texturing and drawing zone and then by intermingling the textured yarns in an air jet-intermingling zone.
Continuous filament heather yarns, which are yarns consisting either of a plurality of continuous filaments of different colours and/or of different dye receptivities so that they are capable of being dyed to different colours, are known in the prior art. The combining of polyester and polyamide yarns to obtain such different dye receptivities in heather yarns is also known. South African Patent Publication No. 73/3977 to Price and Hucklin, laid open for inspection May 29, 1974, discloses a process wherein continuous filament heather yarn is made by both drawing and stuffer box crimping component polyester and polyamide yarn together, followed by two separate intermingling steps. In the first intermingling step, the filaments are intermingled within each yarn, and in the second intermingling step the two intermingled yarns are brought together for entanglement with one another.
A process for making heather yarn by both drawing and jet bulking combined polyester and polyamide yarns followed by one or more intermingling steps is also known in the prior art.
Heretofore, processes for making continuous filament heather yarns in which both polyester and polyamide yarns are false twist textured have involved false twist texturing and drawing the polyester and the polyamide yarns separately, followed by twisting the yarns together to form the completed heather yarn. Such two stage processes in which the polyester and polyamide yarns are false twist textured separately have the disadvantages of requiring additional equipment and of tending to be relatively expensive.
It has now been found that the above disadvantages may be overcome and a process for making heather yarn, by both drawing and false twist texturing combined continuous filament polyester and polyamide yarns, followed by intermingling of the false twist textured yarns in a jet-intermingling zone, may be carried out provided that the polyester yarn fed to the process is a feed yarn having a residual draw ratio in the range of from 1.6 to 2.0 and that the polyamide yarn fed to the process is a feed yarn having a residual draw ratio in the range of from 106 to 120 percent of the residual draw ratio of the polyester feed yarn.
The term residual draw ratio as used herein means the draw ratio required to draw a given partially oriented continuous filament yarn to the conventional break elongation for said yarn after having been draw-textured in a conventional false twist draw-texturing process. For such a draw-textured polyester yarn made from poly(ethylene terephthalate) the conventional break elongation is about 20 percent and for such a draw-textured polyamide yarn made from poly(hexamethylene adipamide) the conventional break elongation is about 35 percent.